News analysis with BESA


How embodied carbon became interesting


Embodied carbon used to be boring. Lacking the glamour and glitz of renewables and emerging green tech, it was often left in the ‘too diffi cult’ box. Not anymore, says BESA’s head of technical Graeme Fox


W


orking out the embodied carbon of a building’s structure has never been straightforward, but it is a walk in the


park compared to the calculations needed to assess the embodied carbon of its services thanks to the complexity of supply chains and technologies. That is why building clients often take the path of least resistance and opt for a ‘statement’ carbon reduction measure like a bolt-on renewable rather than digging too deeply into the maths needed to address embodied carbon that really makes a diff erence. However, times are changing and, although it is a


diffi cult science, calculating embodied carbon is not impossible – and the market now has access to tools that bring ‘true’ lifecycle carbon reduction into reach. Around 50% of the embodied carbon of a building is associated with the structure and can be calculated up-front during construction. The availability of more complete data and better design methods mean designers can now provide compelling arguments for more investment at the front end of projects to signifi cantly reduce the lifetime carbon impact of a building. This is also ramping up pressure on the Treasury


to reform a tax system that currently discriminates against retrofi t and refurbishment – and incentivises demolition and rebuilding. That might have made some sort of sense in the past, but we now live in a world focused on dramatically cutting carbon to address the threat of climate change – and that means we must get to grips with the complex maths needed to calculate the true carbon impact of a building from start to fi nish.


Petition


The controversy around this has become crystallised in one cause celebre building: Marks & Spencer’s fl agship store in Oxford Street. Thousands of people have signed a petition to save the 1920s landmark, which is scheduled for demolition and replacement with a brand-new M&S retail and offi ce building. A report commissioned by SAVE Britain’s Heritage compared the whole-life carbon impact of a comprehensive retrofi t with the current plan to demolish and rebuild. The study carried out by


Nobody said this was going to be easy! During a recent BESA webinar, Simon Wyatt, sustainability partner at the design consultancy Cundall, admitted that embodied carbon used to be seen as “boring because it is about making things work well throughout the year – it is not about green bling”. However, he said there was starting to be more


architect and carbon expert Simon Sturgis said the 10-storey mixed used scheme would result in ‘signifi cantly’ higher carbon emissions and did not comply with Net Zero legislation or the Greater London Authority’s stated policy to prioritise retrofi t. It also fails to meet the London Energy


Transformation Initiative (LETI)’s 2030 targets despite claiming to comply with them. However, Arup had already carried out a


comparative study which showed that, despite there being 40,000 tonnes of embodied carbon in the new build, the replacement project would still result in a smaller carbon footprint over its lifetime. The architect Pilbrow & Partners also compared the new building to a Tesla electric car claiming it would outperform a refurbishment in whole- life carbon terms within 16 years – and planning permission has been granted. Meanwhile, just a few miles away London planning authorities have rejected another colourful, but controversial proposal – the ‘Tulip’ tower designed by Norman Foster – largely on embodied carbon grounds. Housing Minister Michael Gove gave that project the fi nal coup de grace. Nicknamed the Tulip because of its distinctive


design, the 305m tall tower would have been the second-tallest skyscraper in western Europe off ering spectacular views of the city. However, the Minister supported planners’ decision


to reject the project on the grounds that eff orts to minimise carbon emissions during construction “would not outweigh the highly unsustainable concept of using vast quantities of reinforced concrete for the foundations and lift shaft”. So, it’s ‘yes’ to the M&S rebuild, but ‘no’ to the Tulip:


“excitement” around the topic as more clients and engineers woke up to the fact that without more eff ort and innovation focused on embodied carbon and lifecycle building performance, we have little chance of meeting our Net Zero built environment goals.


Comprehensive


CIBSE produced the fi rst comprehensive guidance for calculating the embodied carbon of building services (TM65) last year and this has breathed new life into the complex process of gathering relevant information from all parts of the supply chain. It is also following the publication up with a range of methodologies for separate products and systems that will help project teams provide clients more accurate information to make better decisions. More manufacturers also provide embodied carbon data these days, which helps calculate the impact of their products from manufacture up to installation. However, the big challenge for contractors is how we address complete lifecycle performance so that we can capture the 50% that can’t be nailed down up front. That requires a change of approach for the


UK, which has generally relied on the Building Regulations to be the fi nal arbiter of design choice. All of that is in question now because of the issues revealed by the Grenfell tragedy – and when it comes to embodied carbon, they really are no help at all. “I have given up on the regulations being a driver


for this as they only calculate energy performance on practical completion, and we need a much better metric for calculating operational use,” Wyatt said. “Part L documents look at the energy effi ciency of equipment, but the [Australian] NABERS scheme has shown that improvements do not come from changing the equipment, but from improving the way the building is operated,” he added.


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February 2022


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